This invention relates to the field of fastening devices of the two-part type, particularly those adapted for use in relatively inaccessible locations and which include means to captivate the inaccessible member, for example a screw or nut, against rotation while the other member is rotated to tighten or remove.
More particularly, the invention relates to a captive fastening device for use with electrical units which must be fastened together, such as for example meter cabinets and bus bar terminal boxes. For outside use, such units must be fastened together securely enough to provide a rain tight seal. Accordingly, the fastening device must be reliable, capable of being tightened securely enough to make a water tight seal, and relatively small due to the minimal space available. The fastening devices should also be captively installed, to guard against the possibility of dropping one or both pieces of a two-part fastener and losing it in the interior of the electrical cabinet or terminal box where it could be a dangerous hazard. Preferably, the fastening device should have both pieces of the two-part fastener captivated.
Existing fastening devices of this kind restrain one of the members by holding it captive in a structural unit, but the other member of the two-part fastener is left free. When assembling two units together in close quarters and relatively inaccessible locations, it becomes particularly difficult if the workman has to hold the loose member of the fastening device in one hand while trying to manipulate and position the work pieces or units to be fastened together with the other hand. In many cases, it is desirable and necessary to have both hands free to align the work pieces which are to be fastened together.
The invention described herein holds both members of the fastening device captive, and in place ready for fastening. One is captively mounted in such a way that it may move reciprocally in an axial direction but not rotationally relative to the assembly in which it is held, the other in such a way that it may move rotationally but not reciprocally with respect to the assembly in which it is held.